1. Field of the Invention
The present invention relates to consumption recording systems with remote reading and in particular to consumption recording systems in which planar antennas are used to radiate a signal corresponding to a measured consumption.
2. Description of Prior Art
In blocks of flats or office blocks with a central energy and water supply, it is necessary to record the individual consumption of each and every tenant as regards gas, heating and/or water, as separate items, and to charge accordingly. In view of the rising cost of energy and water and also the very different consumption rates of individual tenants, e.g. singles as compared with families with children, it is no longer supportable to deduct the energy and water costs by a "rule of thumb" based on the rented domestic or business area.
This has led to the provision of a separate meter for electrical energy for each tenant or proprietor, all the meters then being normally located in a common room, e.g. in the cellar of the house concerned. In order to read the consumption data for electrical current, a municipal works employee must take the meter readings at regular intervals, which is not too time consuming since all the house's current meters are located in a common room.
The situation is different, however, in the case of central gas supplies or central heating systems for blocks of flats and office buildings. The system is here usually supplied through a central burner unit, so that it is necessary to affix a heating meter to e.g. each radiator. The situation is similar for a gas supply. Here a gas meter is provided at the entry point of the gas network into the respective flat. In order to record the consumption and to produce a bill, it follows that an employee of the utility company must enter every flat, e.g. to take the gas reading, whereas in the case of heating meters on heaters it is even necessary for the employee of the utility company to seek out each single radiator and each warm water pipe so as to note down the corresponding meter reading in order to provide a complete bill for each residential unit. In view of the great amount of time needed to enter every single flat of a block of flats or even every single room of a flat, reading is very expensive and time consuming. The reading costs may even be of the same order as the total incurred heating costs.
In view of the situation described, efforts are being made to implement a reading of the cited consumption recording devices using wireless telemetry. The linear antennas used hitherto as transmitting/receiving antennas for this purpose, such as e.g. dipole antennas, vertical antennas or loop antennas, suffer, however, from the disadvantage that it is extremely difficult to meet the demands made on wireless consumption recording systems with the cited antenna types. In particular, these demands consist of an adequate transmitting or receiving efficiency and adequate security against destruction and impairment through the environment.
The electrical properties of the cited antenna types change dramatically as soon as conductive material, such as e.g the casing of the meter, comes near the radiating component. Persons skilled in the art also call this the "proximity effect". Thus a vertical antenna e.g. only functions satisfactorily if it is located on the outside of the meter casing, the casing serving thereby as HF counterpoise. With this setup the antenna is accessible from outside and can be damaged very easily.
Furthermore, the wall mounting of such devices presents a fundamental problem because a vertical antenna thereby always finds itself close to the HF-disturbing wall of the house, which may be made of reinforced concrete e.g., or near to a metal radiator or gas meter. The same is true for dipole antennas, since these cannot be mounted sufficiently far from the wall of the house or the radiator. The mounting location also has the consequence that an omnidirectional radiation characteristic of the transmitting/receiving antenna does not necessarily make sense, since electrical energy is radiated unprofitably into the wall, which is fundamentally subject to losses. The linear polarization of the electromagnetic field that the cited antennas radiate also has a disturbing effect since reflections of the electromagnetic radiation are accompanied by rotations of the plane of polarization of the radiation which lead to a reduced receiving power at the input of the receiver.